Various devices, systems and methods have been used to transport, handle and process miniature electronic components such as capacitors and resistors. Miniature electronic components are generally square, rectangular or cylindrical and are typically loaded into a part-handling plate or carrier plate for handling and processing as a batch. Various types of processing operations are performed while components are mounted in carrier plates. For example, external electrodes may be applied to opposite ends of chip components mounted in carrier plates using component termination techniques described in U.S. Pat. Nos. 4,788,931; 4,395,184; 4,381,321; 4,526,129; and Japanese Patent Publication Nos. 61-50365 and 2-83913.
Conventional carrier plates are rectangular and have an array of apertures for resiliently holding miniature components. Carrier plates are substantially rigid to facilitate loading, handling and processing operations, yet the apertures for holding individual components provide resilient gripping means that hold components in a random or predetermined orientation during loading, transport and processing operations. Several different carrier plate designs have been proposed.
Conventional carrier plates are described in U.S. Pat. Nos. 4,526,129; 4,381,321; 4,395,184; and 4,393,808. These carrier plates comprise a rigid metallic plate with a multiplicity of component passageways arranged in an array. The interior portion of the plate is coated with a resilient material such as silicon rubber or a resilient polymeric material that coats both surfaces of the plate and additionally coats the interior surfaces of the passageways. The resilient coating on the walls of the component passageways extends from face to face of the coated plate. The component apertures through the compliant material have slightly smaller dimensions than those of the electronic components, so that the resilient material grips components continuously when they are loaded in the plate. The length of each resilient aperture is greater than the maximum length of parts to be handled using the plate. Various carrier plates are provided for components having different dimensions. In general, each carrier plate has an array of uniformly-sized apertures.
Japanese Patent Publication No. 2-83913 describes a carrier plate similar to those described above, except that the carrier plate has a thickness less than that of the longest dimension of the electronic components. When electronic components are loaded into this type of carrier plate, opposite ends of the components project from opposed surfaces of the carrier plate. This permits modification of various processing techniques.
U.S. Pat. No. 4,598,821 teaches a carrier plate for holding miniature electronic components wherein an elastic sheet is interposed between and bonded to two rigid metallic or plastic plates to form a laminated assembly. A frame is mounted around the laminated assembly. Holes in the elastic sheet are smaller than and centrally aligned with respect to corresponding holes in the rigid plates. The thickness of the laminated assembly is less than the maximum length of parts to be handled so that loaded components project from both surfaces.
U.S. Pat. No. 4,928,821 discloses a carrier plate comprising a rigid base plate having an array of openings and a sheet of elastomeric, resilient material removably attached to one or both surfaces of the base plate. The elastomeric sheet has openings in alignment with but smaller than those of the base plate to resiliently hold electronic components for transport, processing, or the like. The openings in the elastomeric material have slits so that when components are inserted into the carrier plate, the resilient openings can expand to substantially the same dimensions as those of the components.
A composite carrier plate incorporating a central compliant member interposed between two rigid plates and aligned using a spacer component is disclosed in U.S. Pat. No. 4,669,416. The central compliant member may be removed and replaced as necessary.
Japanese Patent Publication No. 61-50365 discloses a method for terminating resistors using a plate body consisting of an elastic silicon rubber. The plate body is provided with an array of apertures for receiving resistors to be terminated. The elastic plate body is thinner than the thickness of the resistors.
Japanese Patent Publication No. 3-76778 discloses a flexible material composed of organopolysiloxanes and a platinum compound employed as the resilient material in carrier plates. The flexible material purportedly has advantageous adhesive and dimensional tolerance properties.
Although conventional carrier plates generally provide satisfactory resilient holding means, they require costly high precision fabrication and assembly techniques. The resilient coating material degrades over time, and such degradation may be hastened by exposure to certain chemicals, fumes, light, repeated thermal cycling and the like. Moreover, sharp edges and corners of electronic components may damage the resilient material coating the carrier plate apertures during loading and manipulation of components in the carrier plates. Furthermore, because components are typically loaded into the carrier plates in the same orientation, the resilient coating becomes worn and loses its resiliency in areas where it repeatedly contacts component edges and corners.
Reconstruction of worn or damaged carrier plates involves removal and replacement of all of the resilient material and is a time intensive and expensive process. Carrier plates are generally treated as a consumable item and worn carrier plates are simply discarded. Substantial efforts have therefore been directed to providing carrier plates having prolonged useful lives.
Component loading systems have been developed to load and align a plurality of components simultaneously in all of the apertures of a carrier plate. As described in U.S. Pat. No. 4,526,129, components are typically loaded into carrier plates using a vibrator and vacuum device that draws components into the apertures formed by resilient material. A loading plate having an array of apertures corresponding to the array of apertures in the carrier plate is typically used to prealign the components for loading into the carrier plate. Loading or holding plates having various configurations are described, for example, in U.S. Pat. Nos. 4,903,393 and 4,847,991.
Conventional carrier plates are rectangular and have dimensions of about 5.times.9 inches and 7.times.11 inches. The size and pattern of apertures varies, depending upon the dimensions of components. Most commercial carrier plates have on the order of about 300 to 5,300 individual component apertures arranged in an array. Component loading and processing apparatus is adapted to match the size and configuration of the carrier plate apertures and requires adjustment each time a carrier plate having a different configuration is used.
Since electronic components are typically handled and processed in batch fashion, increases in throughput are generally attributable to reductions in the time required for a particular processing operation, or to conventional processing of larger batches. For most component processing operations, the processing time is substantially the same, regardless of the number of components in the batch.
There are limitations, however, on the dimensions and configurations of carrier plates and the processing equipment adapted to hold and manipulate loaded carrier plates. Carrier plates larger than the conventional rectangular plates are prone to excessive warpage, even during routine handling and processing operations. Warpage may be even more pronounced as a result of repeated thermal cycling of carrier plates. Use of warped carrier plates results in inaccurate component positioning and unsatisfactory component processing results. Moreover, for carrier plates that are coated with resilient material using various bonding techniques, larger surface area coverage requirements are difficult to achieve within prescribed tolerances.
There is thus a need in the art to provide improved carrier plates having enhanced component capacity that increases the overall component handling and processing throughput. Carrier plates having a prolonged useful life would also be desirable. Such improvements must be achieved without reducing the rigidity and structural integrity of the carrier plate.